Plasma gasification reactors (sometimes referred to as PGRs) are a type of pyrolytic reactor known and used for treatment of any of a wide range of materials including, for example, scrap metal, hazardous waste, other municipal or industrial waste and landfill material, and vegetative waste or biomass to derive useful material, e.g., metals, or a synthesis gas (syngas), or to vitrify undesirable waste for easier disposition. In the present description “plasma gasification reactor” and “PGR” are intended to refer to reactors of the same general type whether applied for gasification or vitrification, or both. Unless the context indicates otherwise, terms such as “gasifier” or “gasification” used herein can be understood to apply alternatively or additionally to “vitrifier” or “vitrification”, and vice versa.
PGRs and their various uses are described in, for example, U.S. Pat. No. 7,632,394 by Dighe et al., issued Dec. 15, 2009, entitled “System and Process for Upgrading Heavy Hydrocarbons”; U.S. Patent Application Publication No. 2009/0307974 by Dighe et al., entitled “System and Process for Reduction of Greenhouse Gas and Conversion of Biomass”; and U.S. Patent Application Publication No. 2010/0199557 by Dighe et al., entitled “Plasma Gasification Reactor”, all of which are incorporated by reference herein for their descriptions of PGRs and methods practiced with them.
Heat from an electric arc can be fed into a cupola, furnace, or other reactor vessel to enhance the operation thereof by providing a very hot gas stream which may be either oxidizing or reducing and can also be mixed with particulate material. The electric arc can be produced in a plasma torch in which the electric arc ionizes the gas which is blown out of the end of the torch producing a hot gas stream which generally operates in the range of, for example, 10,000° F. or 5,538° C.
Heat from an electric arc can be relayed by means of superheated gas (plasma) to a gasifier or furnace. A feed nozzle, as described in U.S. Pat. No. 4,761,793 can be used to direct a large amount of thermal energy to a cupola or other furnace. The feed nozzle described in U.S. Pat. No. 4,530,101 is effective, but is limited in terms of functional length (i.e., the distance between the plasma torch from a coke bed in the gasifier or furnace is limited). To relay thermal energy from a plasma torch, a feed nozzle with a tubular or conical chamber can be used in conjunction with a shroud gas that separates the superheated gas flow from the walls of the chamber. It is desirable to ensure that the superheated gas flow remains axial in relation to the chamber length otherwise impingement of the superheated gas flow on the chamber wall can cause mechanical failure of the chamber wall. The chamber wall is typically water cooled and cast in a refractory. At longer lengths of this chamber, more energy is lost from the superheated gas flow to the water cooling of the chamber wall. This thermal loss to water cooling reduces the efficiency of the overall process.